Refractive surgery Flashcards
when shouldn’t u have refractive surgery
unstable ametropia only 1 seeing eye irregular corneal surface viral infections pregnancy drugs/steroids which affect healing response inappropriately motivated
What does px need to do for the initial assessment
leave out cl RG- a month soft- 2 weeks Bring in ur past RX's to show stability asses px's expectations
What do u check pre-surgery
Visual function- Va- Rx- cyclo? fields Fundus examination Anterior examination IOP CONSENT pupil diameter pachymetry biometry corneal topography tear film quality aesthesiometry- corneal sensitivity muscle balance amp of accom
What base do u need when correcting on cornea
Myopes need BASE IN
Hyperopes get BASE OUT
What’s the relative contact lens magnification
CLM- 1- d*Fsp
What happens to IOP levels after surgery
After myopic laser surgery- IOP reduced
after corneal grafts- increased
NOT the actual IOP measurement but due to the
What’s keratoplasty
Corneal graft
Could be full- penetrating
or partial
A donor cornea is used when host tissue is diseased. Sutured up.
Lamellar Refractive Keratoplasty
can either have
keratophakia- donar/synthetic lens for cataract px
keratomileusis- slicing into cornea then reshaping it- for myopic px
epikeratoplasty- donor cornea- epithelium grows over graft to correct hyperopia
What’s keratectomy
TO CORRECT ASTIGMATISM remove tissue crescent piece of corns cut residual sutured steepening in that meridian Photorefractivfe keratectomy- light energy used to remove tissue
What’s keratotomy
cutting into cornea incisions not on visual axis obis cornea can be weak due to this trauma may cause a globe rupture 2 types: RK radial patterns for spherical correction- flattening cornea and AK astigmatic keratotomy where transverse patterns for astigmatism cut
what’s thermal kerotoplasty
the remoulding of the cornea
heating probe applied in mid- peripheral cornea-
localised shrinkage go collagen- therefore central steepening- hyperopia
can use Nichrome (NiCr) wires- 600degrees for 0.3secs-probs include unstable rx, recurrent erosions, scars, necrosis, vascularisation or YAG Holmium laser at 60degrees or even conductive keratoplasty- which use radio waves at 65degrees for 0.6seconds.
what do u do to each refractive error in refractive surgery
myopes- flatten- ablate- remove tissue
hyperopes- ablate mid-peripheral- which steepens- u have changed contour
whats an excimer laser
EXcided dIMER
Cold laser- vaporise tissue
Breaks molecular binds in cornea- initially KrF-248 now ArF-193nm.
initially for computers.
first used for keratotomy X didn’t work as u ablated tissue. so used in photo refractive keratectomy then lasik/ lasek
tell me about PRK
insert speculum put anaesthetic get them to look at a target then u remove epithelium with either alcohol/manual blade? or even a mechanical rotary brush this weakens epithelium dry corneal bed ZAP
Gives u uneven thickness- unpredictable results
after op- re-epithalised and PAIN
antibiotics, steroids?
ocular lubricants?
Va could be poor- stable after 6-12 weeks
what happens in lasek- what faisal has- faisal flap- ff- ffs- ff- flap- lasek
well epithelium is weakened with alcohol also but instead of being removes,
its scraped to one side
then re put over like a sort of bandage
this gives less pain, quicker recovery
